Thermal expansion of Li0.9Mo6O17 is a-axis dominated which reduces the separation of the conducting chains at low temperature enhancing the interchain coupling. This destabilizes the Luttinger-liquid fixed point leading to an electronic charge- (or spin-) density wave dominated by Coulomb repulsion, as predicted by theories for Luttinger liquids.

A new method for analyzing second-order phase transitions is presented and applied to the polaronic system La(0.7)Ca(0.3)MnO3. It utilizes heat capacity and thermal expansion data simultaneously to correctly predict the critical temperature's pressure dependence. Analysis of the critical phenomena reveals second-order behavior and an unusually large heat capacity exponent.

Despite the rapid development and enormous success of organic–inorganic hybrid halide perovskites (AB′X 3), such as CH3NH3PbI3 as absorbers for perovskite-based solar cells (PSCs), the commercial applications of photovoltaic techniques still face several challenges, such as decomposition when exposed to light and moisture, and lead toxicity. On the other hand, the double perovskites (A 2 B′B″X 6) are derived from the AB′X 3 when half of the octahedrally coordinated B′-cations are partially replaced by the suitable B″-cations. They are attracting attention due to a new design strategy to replace Pb2+ ions with the couple of a monovalent M + ion and a trivalent M 3+ ion, leading to a new family of quaternary double perovskites. In this way, we aim to synthesize and characterize Cs2AgSbCl6 powdered samples, designed for solar cell applications. The crystalline phase and morphological features are investigated by X-ray powder diffraction (XRPD), neutron powder diffraction (NPD), scanning electron microscopy (SEM) in complement with UV–vis spectroscopy, showing a suitable band gap of 2.7 eV. The solution synthesis method proved to be efficient in obtaining polycrystalline-Cs2AgSbCl6 samples in a cubic ordered phase. DFT calculations also provided insights on the vibrational properties of Cs2AgSbCl6, corroborating the experimental data and elucidating the optical activity of Raman and infrared modes.

Magnetic measurements of La 0.7 Ca 0.3 MnO 3 reveal a departure from Curie-Weiss behavior below the orthorhombic ͑O͒ to rhombohedral ͑R͒ structural transition at T O−R = 705 K. Between T O−R and T ‫ء‬ = 273 K, the magnetic response is clearly paramagnetic but with an enhanced magnetic moment attributed to the existence of small ferromagnetic polarons. These polarons grow in density and begin to interact below T ‫ء‬ as evidenced through low-field magnetic-susceptibility and field-dependent magnetization measurements, which show hysteresis and saturation, respectively. At the ferromagnetic transition temperature T c = 247.1 K, the polarons coalesce and the system exhibits long-range ferromagnetism. It is asserted that the transition at T c should be viewed as a polaronic to ferromagnetic phase transition. The relevance of the Griffiths phase is addressed.

The structural, magnetic, and transport properties of single-crystalline Lu 2 V 2 O 7 are studied. Lu 2 V 2 O 7 shows a ferromagnetic transition at T C = 69.5 K and a negative magnetoresistance ͑MR͒ as high as 50% at T 2 = 75 K with an applied field of 5 T. Through various experiments, it is demonstrated that the mechanism for MR is not through double exchange, but through a polaron-mediated behavior similar to Tl 2 Mn 2 O 7 . This places Lu 2 V 2 O 7 as the only other example of polaron-mediated MR among the pyrochlore oxides.

No abstract

Methylammonium lead iodide (MAPbI3) is an important light-harvesting semiconducting material for solar-cell devices.

High-resolution synchrotron x-ray diffraction measurements were performed on single crystalline and powder samples of BiMn 2 O 5 . A linear temperature dependence of the unit cell volume was found between T N = 38 and 100 K, suggesting that a low-energy lattice excitation may be responsible for the lattice expansion in this temperature range. Between T* ϳ 65 K and T N , all lattice parameters showed incipient magnetoelastic effects, due to short-range spin correlations. An anisotropic strain along the a direction was also observed below T*. Below T N , a relatively large contraction of the a parameter following the square of the average sublattice magnetization of Mn was found, indicating that a second-order spin Hamiltonian accounts for the magnetic interactions along this direction. On the other hand, the more complex behaviors found for b and c suggest additional magnetic transitions below T N and perhaps higher-order terms in the spin Hamiltonian. Polycrystalline samples grown by distinct routes and with nearly homogeneous crystal structure above T N presented structural phase coexistence below T N , indicating a close competition amongst distinct magnetostructural states in this compound.